Levels of Organization

• Molecules• Cells• Tissues (next slide)

• Organs• Organ systems• Organism• Population• Community• Ecosystem• Biosphere

• Molecule

– The smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms held together by chemical forces

• Cell– The basic unit of structure and function for all

living organisms

Tissues and organs• Tissue

– An anatomical unit composed of cells organized to perform a similar function

• One kind of cell makes up tissue

• Organ

– An anatomical unit composed of tissues serving a common function

• Consists of different tissues

• Organ System– An anatomical system composed of a group of organs

that work together to perform a specific function or task

• Organism– A form of life; animal, plant, fungi, etc.

• Population– A group of individuals of the same species

living in a specific geographical area and reproducing

• Community– Different populations of organisms interacting

in a shared environment

• Ecosystem– A system composed of organisms and nonliving

components of an environment

Biome – a large area or geographical region with distinct plant and animal groups adapted to that environment

Biosphere – the zone of life on earth: sum total of all ecosystems on earth

The history of the cell

• Exploring the cell…

A Time line

• 1665 Robert Hooke-looked at cork using one of the first

microscopes.

• Coined the term “cells”

1674 Anton van Leeuwenhoek – views tiny living organisms in pond water.

1831 Robert Brown – discovered the cell’s nucleus

1838 Matthias Schleiden – concludes that all plants are made up of cells.

1839 Theodor Schwann – concludes that all animals are made up of cells

1855 Rudolph Virchow – proposes that all cells come from existing cells

Cell Theory

• Completed in 1855

1. All living things are made of one or more cells.

2. Cells are the basic units of structure and function in living things

3. All cells come from other cells

Prokaryotes and Eukaryotes

• The two main cell categories

• Classified on whether they contain a nucleus or not.

Prokaryotes• Do Not contain a nucleus

– DNA within the nucleoid region

• No membrane bound organelles

• DNA spread throughout the cell

• Contain a cell membrane

• Contain a cell wall

• Contain ribosomes

• Bacteria are prokaryotes

• Label the prokaryote cell with the following

– DNA (nucleoid region), ribosomes, cell wall, cell membrane, flagella, pili

Images of Bacteria - Prokaryotes

Soil bacteriaPseudomonas aeruginosa

E. Coli

Staphylococcus aureus

Endosymbiosiseukaryotic cells were formed from simpler prokaryotes

• Endo – within

• Symbiosis – together– Organisms living together, within one another

– Bozeman science video-endosymbiosis

https://www.youtube.com/watch?v=-FQmAnmLZtE

Eukaryotes

• Contain a nucleus– Contains genetic material (DNA) inside.

• Contain membrane bound organelles

• All have a cell membrane

• Contain ribosomes

• Some have a cell wall

• Generally larger than prokaryotes

Eukaryote Cells

plant

Animal

Examples of eukaryotes

• Some Eukaryotes are single-celled organisms

Plants, animals, fungi and protists are examples of multicellular eukaryotes.

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